Pianos are not the only item subject to this scam.  The scammers will
test the waters for any expensive item being advertised.  What they do
is promise to pay in advance with a cashier's check.  They tell you
that once you receive the check you can send the item.  But then comes
the rub.

They will overpay you some amount in order to facilitate the sale.
They then ask you to refund that amount.  The problem is that the
cashier's checks frequently look good enough to fool a bank, at least
for a few days.  Then it will be returned as being a fraudulent check.
You are then out the amount of money you refunded and also the amount
your bank charges you for a bounced check.

Steer clear and stay safe.

Paul Meehan